Be careful what you wish for.
If you were able to treat the stocks that you purchased as investments as inventory, you would presumably need to treat all of them similarly. So if you sold them at a gain, that would also end up being ordinary income rather than (long term?) capital gains. But I think that would be a moot point under the circumstances anyway.
Maybe I'm missing something, but the only benefits of treating them as inventory (and thus the trading as a business) is that (1) You are not subject to the $3,000 limit on offsetting other income. (2) Better deductibility of certain investment expenses.
The downside is that any gains you make would be subject to (1) Ordinary income tax rates (2) Self employment tax?
Presumably you would expect there to be more gains than losses, so this doesn't seem like something you would want to do unless you had to....